The present invention relates to an inspection system for packaged integrated circuits. The present invention has particular applicability in inspecting stacked integrated circuit packages prior to shipping the stacks to users.
Conventional packages for semiconductor devices, also known as integrated circuits (xe2x80x9cICsxe2x80x9d), include thin small outline packages (TSOPs) having leads, or ball grid array packages (BGAs) having attached solder balls. Typically, packaged ICs are electrically tested, then placed in JEDEC standard plastic trays having an array of pockets for holding the devices, such as an 8xc3x9712 array of ICs. For example, 10 trays may be filled with ICs and stacked, with an empty tray put on top. The stack of trays is then strapped together, as with four plastic straps.
The stack is then transported to a marking station, where an operator removes the straps. The trays are automatically singulated, the ICs are marked, and the trays are automatically re-stacked (i.e., 10 full trays plus the empty tray on top). Next, the leads or solder balls are inspected at an inspection station, and the inspected ICs are then baked in an oven, such as at about 125 degrees Centigrade for about 4 hours, depending on the package type. After the trays cool, the stacks are separated into stacks of about 5 trays. The trays are visually inspected by an operator for ICs that are misplaced in the trays (i.e., not seated properly in the pockets), and then strapped again, as by an automated strapping machine, and packed for shipping to a user.
Disadvantageously, operator error during visual inspection is time-consuming, and allows tray stacks with misplaced ICs to be strapped and shipped to the user, resulting in the user receiving damaged ICs with bent leads, non-planar leads, etc.
There exists a need for a method and apparatus for quickly and reliably inspecting stacked trays for misplaced ICs, thereby reducing manufacturing costs and preventing damaged ICs from being shipped to the user.
An advantage of the present invention is a method and apparatus for fast and thorough inspection of tray stacks for misplaced ICs that is not susceptible to human error and prevents shipment of damaged ICs to users.
Additional advantages and other features of the present invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the invention. The advantages of the invention may be realized and obtained as particularly pointed out in the appended claims.
According to the present invention, the foregoing and other advantages are achieved in part by an apparatus for inspecting a stack of trays containing articles, each tray having a plurality of pockets, each pocket being for holding one of the articles in a predetermined position, the apparatus comprising a sensor, movably mounted adjacent to the stack, for generating a first signal when the articles in one of the trays are in the predetermined position, and for generating a second signal when one of the articles in one of the trays is not in the predetermined position; a motor for moving the sensor relative to the trays; and a processor for generating an alarm responsive to the second signal.
Another aspect of the present invention is method of inspecting a stack of trays containing articles, each tray having a plurality of pockets, each pocket being for holding one of the articles in a predetermined position, the method comprising providing a sensor, movably mounted adjacent to the stack, for generating a first signal when the articles in one of the trays are in the predetermined position, and for generating a second signal when one of the articles in one of the trays is not in the predetermined position; moving the sensor relative to the trays; and generating an alarm responsive to the second signal.
Additional advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment of the present invention is shown and described, simply by way of illustration of the best mode contemplated for carrying out the present invention. As will be realized, the present invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.